Filled paper



ECS

FILLED PAPER Leon J. Paquin, Glens Falls, N.Y., assignor to The National Cash Register Company, Dayton, Ohio, a corporation of Maryland 1 Claim. (Cl. 162-181) This invention relates to new and useful improvements in filled papers and particularly seeks to provide paper containing filler materials of such a nature that the formed paper sheets are capable of being used as sensitized record material of the type that produces a color reaction when subjected to printing or other type of characterforming operations with color-reactant materials.

This is a division of my copending application which issued on July 31, 1956, as United States Letters Patent, No. 2,757,085.

Sensitized record materials to which this invention generally relates may be described as comprising a base sheet which carries a normally colorless reactant capable of reacting with a second, normally colorless reactant associated therewith whereby to cause the two reactant materials to produce color upon the practicing of any printing or other character-forming operations thereon.

This invention particularly provides a novel paper sheet for such sensitized record materials which has bodily incorporated therein as a filler certain materials which in themselves are normally colorless but which are capable of reacting with a second normally colorless material to produce color on the sheet as the direct result of practicing printing or other character-forming operation thereon.

This invention also provides a novel filled paper sheet in which the color-reactable filler materials were added to an aqueous pulp suspension prior to the time at which a sheet or web is formed whereby to assure the even distribution of the filler materials and their reaction products throughout the finished web and to coat the individual pulp fibers without causing the formation of localized areas of solidified or flocced filler.

More specifically, the sensitized paper sheet produced in accordance with this invention is particularly adapted for use in connection with organic color-reactable materials such as the phthalides disclosed in United States Letters Patent 2,505,470, granted to B. K. Green, April 26, 1950.

In the particular type of color reaction in which the novel paper of this invention plays a part, fine particles of solid inorganic material, providing a large adsorbent surface area, form one of two color reactants, and this material is adapted to cause a color change in certain organic compounds coming into adsorption contact therewith. The organic compounds may be those disclosed in the above mentioned patent and may be used either in fluid or solid form, but if in solid form preferably should be carried in a fluid vehicle to promote the ad: sorption contact, and include such compounds as crystal violet lactone and malachite green lactone. Crystal violet lactone is the 3,3 bis(p-dimethylaminophenyl)-6-dirnethylamino phthalide as disclosed in United States Reissue 23,024, issued to Clyde S. Adams on August 17, 1948.

An object of this invention, therefore, is to provide a paper sheet filled with an adsorbent inorganic colorreactable material suitable for use as sensitized record materials.

Another object of this. invention is to provide a paper sheet of the character stated in which the filler comprises a mixture of sodium aluminate, sodium silicate and their reaction products.

A further object of this invention is to provide a paper sheet of the character stated in which a relatively intense, clear color will appear as the result of printing or other character-forming operations when used in conjunction With a suitable organic color-reactable material.

A further object of this invention is to provide a paper sheet of the character statedin which the color produced will remain without fading for substantial periods of time.

With these and other objects, the nature of 'which will become more apparent, a fuller understanding of this invention will be gained by reference to the following detailed description and the appended claim.

Heretofore other workers in the art have had some success in producing coated paper for use as the base sheets in sensitized color-producing record materials, but it has been considered impossible to employ filled sheets for the same purpose in view of the fact that only a small fraction of the filler material would be available on the surface of the sheet for contact with the organic colorreactable material, whereas in the coated sheets a large part of the inorganic color-reactable' material is available on the surface of the sheet.

For the first time this invention has solved the problem of how to make a filled sheet completely suitable for use as color-reactable sensitized record materials.

In accordance with the principles of this invention it has been found possible to produce a paper sheet filled with an inorganic material, namely, a mixture of sodium aluminate (NaAlOg), sodium silicate (approximately Na O-3.2SiO and any reaction products thereof, particularly useful as a base sheet for color-reaction with many organic color-reactable compounds.

A paper sheet may be made in several ways in accordance with this invention and it is believed that the following examples will serve adequately to illustrate the,

of bone-dry pulp per weight of pulp and water) at ordinary temperatures was added 41 cc. of a freshly pre-. pared 10% solution of sodium aluminate by weight.

based on bone-dry pulp) with constant stirring. After the addition of the sodium aluminate was completed 41 cc. of a 10% solution of sodium silicate (15% by weight based on bone-dry pulp) was added with constant stirring. The resultant mixture was diluted with water to a volume of 2 liters in order to provide practical volumetric units when sheets are made. values are generally on the order of 10 to 12. The. mixture is then adjusted to a pH of 6.0 to 6.2 with-a 10% solution of papermakers alum. Hand sheets were then made in a sheet mold, having a cross-sectional area of 31 sq. in. and a volumetric capacity in excess of 4.1iters, :byv

pouring a 50 cc. quantity of the above suspension into the mold in which there is sufiicient water to bring the volume to 4 liters, adjusting the pH to a value of about 6.0 by

the addition of 0.08% alum solution, and then forming the sheet.

The resultant sheets of 31 sq. in. area each weighed about 0.9 gram (27.6 pounds on a 24 X 36'500 basis) tone of the type disclosed in United States Patent 2,374,- 862 as an emulsion containing tetra-methyhdiamino At this stage the pH diphenyl phthalide, granted to B. K. Green on May 1, 1945, exhibited intense color and clear-character formation when subjected to the action of a dry-faced adding machine printer or of a typewriter.

A "more specific formula for malachite green "lactone is 3,3 ibis (p-Idime'thylaminophenyl) :phthalide. Thematiachite :green lac'tone 1 gives a green color when 'chang'e dto its colored form. Other color reactants are suitable, such as crystal violet lactone, which has the formulal3,3 bis (ip-dimethylaminophemtl) .6 .-dimethylaminolphthalide, produces a dark blue color when changed to the colored form.

Example 2..'-.;Another 500 .cc. of the samepulp :suspension was treated exactly as in Example 1 above, but the pH in 'the sheet mold was adjusted to-a value of about 5;.0.

vEllie resultant sheets contained from about 16% to 19% alurnino-silicate filler. Each of these sheets'when used with a second sheet coated with the emulsion coating containing malachite green lactone or crystal violet lactoneiexhibited amore'intense color than that secured in Example -1 with .the same clarity of character formation when subjected to the action of a dry faced adding machine printer-or of a typewriter.

In the :foregoing examples 'the'nature of the filler retained in the finishedsheets was 'determined through the use of a pulpless system in which the quantities of chemica1s,'concentration of chemicals, successive dilutions and pH control were the same as for making handshee't s. Thus 4.08 grams of air'dry sodium aluminate were dissolved in 40 cc. of hot water and added to 473cc. of water. Then 40.8 cc. of the approximate composition Na O-lZSiO was added under continuousstirri-ng to the sodium' aluminate solution. The mixture was then diluted to a volume of 1800 cc. and'95 -cc.-o'fa 10% alum "solution was added to lower the pH from approximately 11 to 6 6.2. The mixture was then transferred to a 2-lit er volumetric fiask and made up to volume. Following this the mixture was poured into an open vessel and, while under constant'stirring, a 100 cc. aliquot was withdrawn, diluted to 1 liter and filtered under vacuum on a tared #41 filter paper. Air-dry,'bonedry and ash weights were obtained on the reissue. Gravimetric analysis indicated the a'lumino-silicate portion of the bone-dr-y filler to be of composition A1 1.85SiO -'3.15=H O. The air-dry (50% RH. at 72 F.) filler contained 23% m'oretree water.

It will be appreciated that-other methods of analysis might produce difierent numerical results as to the amounts of retained filler -in the finished sheets as well as variations in the indicated composition of the retained filler.

The foregoing two examples represent what now appears to be the optimum pecentages of the added filler materials-'atpH valuesof 5 to 6 which are values that can be :satisfactorily employed under standard mill procedures onfull-scale runs.

ltshould be noted that within a wide range-of'total percentages of fillers used, based on pulp, a one to one ratio as between the sodium aluminate and the sodium silicate gives the best results with respect to color sensitivity of the finished sheet, but usable results as to color sensitivity are obtainable with the use of one part-of'sodium aluminate and from 0.7 to 2.0 parts of sodium silicate.

Surprisingly it has been found that to a considerable degree the color sensitivity and uniformity of these filled papers is dependent on the manner in "which the filler compounds are added to the pulp suspension. It will be noted from the preceding examples that perfectly satisfactory results are obtainable when thesodium aluminate is added to the pulp suspension first followed by addition of the sodium silicate and pH adjustment with alum water.

When this procedure is followed the individual'fibers of 4 the pulp apparently become coated with the filler materials or the reaction products thereof-and consequently the retained filler is uniformly distributed in fine particle form throughout the finished paper sheets.

However, when the order of addition of filler was reversed and the sodium silicate added first followed by the sodium aluminate the resultant paper sheets were not as satisfactory from the standpoint of color sensitivity. Similar troubles were encountered when attempts were made to form a clear fluid gel from the sodiumaluminate and sodium silicate and then adding the gel to the pulp suspension.

In View of the fact that many variables will beencountered from time to time during the manufacture of filled color-sensitive papers of this type the quantities, consistencies, pH values, etc. given above should be recognized as illustrative only. Whenever changes are made in the specifications for the finished sheets in accordance with various end uses such changes invariably will require a change in the -freeness of the pulp, for example, and a change in freeness in turn could well modify the amount of filler retained if the same gross amount of filler were added. Therefore, the quantities of sodium aluminate and sodiunr silicate would have to be changed from those given in the above examples in order 'to secure the same color sensitivity in the finished sheets. Similarly, variations in the nature of the wood pulp itself, for example, use of a furnish of "bleached sulphate pulp, or a mixture'o'f bleached groundwood and sulphite pulps in place of all bleached sulphite stock will necessitate corresponding changes. rectamounts of the sodium aluminate and sodium silicate to be added will be for'economical purposes the smallest amounts consistent with the obtaining of satisfactory color sensitivity inthe finished paper.

In a machine run of paper made in accordance with this invention the filler materials are added tothe pulp suspension at any convenient place in the system and the pH subsequently adjusted as in the foregoing -ex amples. For illustrative purposes 15% by weight (based on bone-dry pulp) of the sodium aluminate solution may be added to the beater and followed by addition of 15 by weight (based on bone-dry pulp) of the sodium sili cate solution.

as at a stock chest, regulator chest, fan'pump or even at the' paper machine head box.

What is claimed is:

A new article of manufacture comprising a sensitizedcolor-reactable paper made of wood pulp fibers coated by having sodium aluminate and sodium silicate added to a water suspension of the wood pulp 'fibers of which the paper is made, in that order, and by causing the sodium aluminate and the sodium silicate to react in the presence of the fibers by the pH adjustment of thej suspension to a value 5-6 with alum water to produce on the fibers the reaction product, alurnino-silicate,

whereby to produce'a finished paper containing not less than 16% air dry (50% relative humidity at 72 degrees Fahrenheit) alumino-silicate on the pulp fibers thereof.

References Cited in the file'of this'patent UNITED STATES PATENTS In any event the cor- ThepH adjustment to 6.0-6.2 through-the use of alum is later made at any convenient place in thesystem between the heater and the paper machine, such Rinman Sept. 27, 1932 Great Britain June 24,1 49 

